Turning tools of the above generally mentioned type are usually used for machining workpieces of metal, preferably by parting, grooving and profile turning. For turning operations, it is desirable to use as slender cutting inserts as possible, in order to generate the thinnest possible grooves, thereby minimizing material losses and energy consumption. This means that the front portion of the support part under the cutting insert, as well as the front finger of the tightening part above the cutting insert have to be designed utmost slender or thin to be accommodated in the groove in the workpiece recessed by the cutting insert. In practice, therefore, the front portions of the support and tightening parts are blade-shaped, even if the rear portions of the parts may have a successively increasing thickness with the purpose of providing optimum stability of the cutting insert.
As a consequence of, on one hand, the fact that the front portions of the support and tightening parts have to be slender, and on the other hand, the fact that the movable tightening part exclusively is connected to the rest of the basic body via a thin, elastically resilient material portion serving as a joint for the tightening part, difficulties arise in cooling the cutting insert in an efficient way. Thus, the cooling of previously known turning tools of the kind in question has been effected in an inefficient and almost provisional way, more precisely by means of two pipe conduits routed from the rear fixing part of the basic body (or a tool holder connected with the same), situated externally to the basic body, and ending in outlets situated fairly far from the cutting insert. De facto, an upper conduit for cooling the cutting insert from above mouths approximately in flush with the topside of the tightening part, while a lower conduit intended for cooling the cutting insert from below mouths at a point situated approximately halfway between the cutting insert and the underside of the support part. In order to improve the cooling of the cutting insert and furthermore avoid the need of the space-requiring external pipe conduits and associated problems, attempts have been made to form the requisite cooling-liquid conduits in the form of internal channels in the proper basic body. However, these attempts have had limited success in that internal channels having a sufficient cross-section area indeed have been producible in the support part stiffly integrated with the fixing part, but not in the pivotably movable tightening part, which, with the exception of the thin, elastic joint, is spaced-apart from the fixing part as well as the support part via open gaps. In other words, it has previously only been practically possible to provide undercooling of the cutting inserts via internal cooling-liquid channels, but not overcooling.
Also, the cooling of the previously known tools has been effected using large quantities of flushing low-pressure liquid (about a pressure of 10 bar), in spite of the development of the cooling technique within the area of cutting machining increasingly being pushed in the direction of using high-pressure liquid. Thus, recently numerous tools for chip removing machining have been designed for cooling-liquid pressures within the range of 400-1000 bar or more.